1. Field of the Disclosure
Embodiments disclosed herein relate to the production of linear alpha olefins. More particularly, embodiments disclosed herein relate to the production of linear alpha olefins, such as hexene-1, from a mixture of internal- and iso-olefins, such as isohexene, 2-hexene, and 3-hexene.
2. Background
There is a growing need for terminal (alpha) olefins such as 1-hexene. 1-hexene may be produced by the selective oligomerization of ethylene, for example. In general, the oligomerization is conducted in the presence of a homogeneous catalyst, such as an alkylated metal catalyst. Long residence times are used to produce hydrocarbon chains of varying lengths. Ethylene oligomerization produces a wide spectrum of linear alpha olefin products, including 1 butene, 1 hexene, 1 octene etc. In addition, depending upon the catalyst used, there are internal olefins such as 2-hexene, 3-hexene, and iso-hexene.
Alpha olefins may also be produced by the isolation of the alpha olefin from a hydrocarbon stream containing a relatively high concentration of the 1-isomer. However, such streams often contain numerous components having a similar or close boiling point to that of the desired 1-isomer.
Alpha olefins, specifically 1-butene and 1-hexene, can be produced from C4 streams utilizing metathesis in combination with double bond isomerization. U.S. Pat. No. 6,727,396 describes such a process and is incorporated herein by reference. A critical step in that process is the removal of isobutylene prior to the metathesis step to avoid the production of isohexenes that would represent a contaminant in a 1-hexene stream to be used as a comonomer in polymerization processes.
Regardless of the source of mixed hexenes, production of comonomer grade 1-hexene requires the removal of the isohexenes and the separation of the internal hexenes. Extensive fractionation is required to separate the alpha olefins having different internal or iso-olefins. Further, given the very low relative volatility between certain of these isomers, fractionation is impractical. Accordingly, there exists a need for processes for the efficient production and recovery of 1-hexene from mixed hexene streams.